1. Field of the Invention
The present invention relates to a composition for a silicone resin. More specifically, the present invention relates to a composition for a silicone resin having excellent transparency and high strength and flexibility, and a composition for a silicone resin having excellent transparency, high adhesiveness and tensile shearing strength, and excellent heat resistance. Also, the present invention relates to a silicone resin composition obtainable or obtained by reacting the composition and a method for producing a silicone resin composition, and a formed article made of the silicone resin composition.
2. Discussion of the Related Art
In the recent years, since silicone resins have excellent heat resistance, durability and weathering resistance, the silicone resins are increasingly used under severe operating environmental conditions. Especially, the silicone resins have excellent transparency because the silicone resins do not have absorption in the visible region, so that the silicone resins are suitably used in applications that require transparency and have severe operating environmental conditions.
For example, polydimethylsiloxanes generally have weak intermolecular forces, so that even when formed into a polymer, they exist in the form of a viscous liquid. In view of the above, as a method of improving strength of a polydimethylsiloxane derivative, a method including the steps of introducing a trifunctional T unit or a tetrafunctional Q unit into a molecule so as to take a cross-linking structure, thereby increasing a degree of cross-linking, and increasing the strength of the polydimethylsiloxane derivative is generally employed (see Japanese Patent Laid-Open No. 2001-200162). A method including the steps of introducing a bulky substituent such as a phenyl group, thereby increasing a degree of crystallization of the resin, and making the resin more rigid is also known (see Japanese Patent Laid-Open No. 2000-265150).
Japanese Unexamined Patent Publication No. 2005-513195 discloses a method of adding a filler to a silicone resin, thereby increasing the strength while keeping flexibility.
In addition, silicone-based pressure sensitive adhesives exhibit excellent moisture tolerance and electric insulation, so that the silicone-based pressure sensitive adhesives are widely used in electronic parts. With the miniaturization of electronic instruments and enlargement in memory capacities in the recent years, further quality improvements in the silicone-based pressure sensitive adhesives are desired because the production steps are complicated.
Conventionally, as a silicone-based adhesive, an adhesive, cross-linked silicone composition or a silicone elastomer or the like derived therefrom is used. However, since a silicone derived from a pure siloxane does not have a sufficient adhesiveness, a method including the step of introducing a functional group such as an epoxy group, an amino group, or a mercapto group into a resin to carry out an organic denaturization of the resin, or a method of subjecting a silicone to a primer treatment using an additive having the functional group is generally carried out (see Japanese Patent Laid-Open No. 2001-200162).
Japanese Patent Laid-Open No. 2000-265150 discloses a silicone composition having a low thermal expansion coefficient and high viscosity by adding silica particles having a small specific surface area. In Japanese Unexamined Patent Publication No. 2005-513195, adhesiveness is improved by using a processing aid such as a plasticizer.
In addition, as an adhesive with increased heat resistance, a silicone adhesive derived from a polyorganosiloxane natural rubber and a cross-linking polyalkoxysilane or the like without subjecting to the organic denaturation as mentioned above is proposed (see Japanese Unexamined Patent Publication No. 2004-502021).